Oscillating dispersed-phase co-flow microfluidic droplet generation: jet length reduction effect.

Area of Science:

• Microfluidics
• Fluid Dynamics
• Materials Science

Background:

• Co-flow droplet generation faces limitations in droplet polydispersity at high throughputs due to jetting instability.
• High dispersed-phase (d-phase) flow rates in co-flow systems lead to unstable jetting, hindering droplet size control.

Purpose of the Study:

• To introduce and evaluate a novel microdroplet generation technique using nozzle oscillation.
• To suppress the jetting effect and improve droplet size dispersity in microfluidic systems.

Main Methods:

• Oscillating the d-phase nozzle within the continuous phase (c-phase) channel.
• Systematically studying the effect of oscillation frequency (0-15 Hz) on jet length under varying d-phase and c-phase flow rates and d-phase viscosities.

Main Results:

• Oscillation significantly reduced jet length, with a maximum reduction of 70.8% observed at high d-phase and low c-phase flow rates.
• Jet length reduction was inversely proportional to oscillation frequency and directly proportional to d-phase flow rate.
• Nozzle oscillation led to the generation of smaller droplets compared to stationary methods and showed potential for simultaneous multi-size monodisperse droplet generation.

Conclusions:

• Nozzle oscillation is an effective active technique to suppress jetting instability in microdroplet generation.
• This method offers improved droplet size control and enhanced throughput, with potential applications in aqueous two-phase systems (ATPSs).